This invention relates to the encapsulation of solar cell arrays and more particularly to a solar cell enclosure and an improved method for encapsulating a solar cell array within that enclosure.
Solar cells or photovoltaic devices are becoming of increasing importance in the generation of electrical power. Individual solar cells are connected in various series/parallel combinations to provide arrays having several output voltage and current options. A module is then fabricated by enclosing a solar cell array between a supportive backplate and an optically transparent glass front plate. The volume between the back and front plates and surrounding the solar cell array is filled with a potting material. A seal between the front and back plates cooperates with the potting material to provide a long-term moisture and contamination barrier. The potting material provides a hydrodynamic cushion for the glass cover plate and provides an adhesive seal with the glass plate, the solar cell array, and the electrical interconnection to the array. The potting material must provide a highly transmissive path for visible light, and a low permeability to typical atmosphere contaminates. It must be dimensionally stable, have a low shear strength, be of high thermal conductivity, and high electrical resistivity. Silicone based polymers that cure into a solid elastomer are often used for the potting material. An alternative which exhibits the desirable properities is the partial crosslinking of silicone monomers such as those utilized in commercial silicone oils. This forms a gel-like material that exhibits excellent cohesive and adhesive strengths. The uncured silicone gel has a consistency similar to that of a medium weight motor oil, and this results in handling problems concerning the containment within the enclosure prior to complete cure. Heretofor, there has not been an effective procedure for potting and enclosing solar cell arrays. Accordingly, it is an object of this invention to provide a solar cell enclosure having a compatible seal design. It is a further object of this invention to provide a solar cell enclosure which has provisions for repairability. It is a still further object of this invention to provide a method for enclosing solar cell arrays. Such a method provides for temporarily sealing the edges of the enclosure during the potting (curing) procedure. The process provides a positive pressurization of the enclosure during the potting process by the hydrostatic pressure of the potting material or by pressurized feeding of the gel into the enclosure cavity. The process further provides the flexibility of adding a second sealant around the panel perimeter prior to the attachment of a spring loaded metal bezel. Still further, the process permits the attainment of less voids in the potting material and imparts a compressive loading on the potting material which in turn minimizes the tendency of the potting material to separate or delaminate from the glass, back plate, or the array surfaces. The enclosure and method provide a highly transmissive, highly adhesive optical coupling of the solar cells to the panel exterior.